Estradiol‐antagonistic activity of phenolic compounds from leguminous plants

Natural flavonoids are currently receiving much attention because of their estrogenic and antiestrogenic properties. Six isoflavones (isoprunetin, isoprunetin 7‐ O ‐ β ‐ d ‐glucopyranoside, isoprunetin 4′,7‐di‐ O ‐ β ‐ d ‐glucopyranoside, genistein, genistein 7‐O‐ β ‐ d ‐glucopyranoside, daidzein), four flavones (luteolin, luteolin 7‐O‐ β ‐ d ‐glucopyranoside, luteolin 4′‐O‐ β ‐ d ‐glucopyranoside, licoflavone C), isolated from Genista morisii and G. ephedroides (two Leguminosae plants of the Mediterranean area) together with two structurally related pterocarpans, bitucarpin A and erybraedyn C, isolated from Bituminaria bituminosa (Leguminosae), were tested for the antagonist activity by a yeast based estrogen receptor assay ( Saccharomyces cerevisiae RMY326 ER‐ERE). Most compounds inhibited the estradiol‐induced transcriptional activity in a concentration dependent manner. In particular, for the flavone luteolin 77% inhibition of the induced β ‐galactosidase activity was observed. Interestingly, licoflavone C exhibited a dose‐dependent antagonistic activity at concentrations up to 10−4 m , but stimulated β ‐galactosidase expression at higher concentrations resulting in a U‐shaped‐like dose‐response curve. Copyright © 2007 John Wiley & Sons, Ltd.